• The color wheel mean Refers to spinning wheel.
• A frequent macOS wait cursor is that rainbow spinning wheel (or whatever you want to name it). It's triggered when an app doesn't react for a few seconds, and it tells you to wait before giving it any additional commands.
• The ball indicates that your Mac is now unable to complete all of the tasks assigned to it. Every application on your Mac has a window server. When an app receives more events than it can handle, the window server displays the spinning ball automatically.

Read More: how do I clean a slow Imac?